1. Field of the Invention
The present invention relates to a planar lighting device and more particularly, to a planar lighting device including a light emitting device.
2. Discussion of the Related Art
Liquid crystal displays (LCDs) which are one type of displays are used in a variety of monitors for televisions, notebook computers and desktops as well as cellular phones.
Such an LCD does not self-emit light, thus requiring a light-emitting device to light a liquid crystal panel so as to display image information.
A light emitting device of LCDs is bonded to a rear surface of a liquid crystal panel and is thus referred to as a backlight unit. This backlight unit forms a uniform surface light source and supplies light to a liquid crystal panel.
A light emitting diode (LED) has a structure in which an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer are stacked in a substrate and an electrode is formed on the p-type semiconductor layer and the n-type semiconductor layer. Regarding a principle of light generation by the light emitting diode, light of the light-emitting layer generated upon recombination between holes and electrons injected from respective semiconductor layers is discharged to the outside.
Such a light emitting diode constitutes a light emitting diode package which is used as a light source of a backlight unit (BLU).
Such a backlight unit provides a planar light source toward the liquid crystal panel, which is thus considered to be an example of a planar lighting device. The planar lighting device is considered to be a light source which uniformly emits light through a flat surface and has a relatively small thickness.
The planar lighting device improves luminous efficacy of a display device and accomplishes structural slimness thereof.
When the light emitting diode is used as a light source of a planar lighting device, the light emitting diode may be a side type in which light is diffused to a side direction or a direct type in which light is emitted in a front direction. A method for uniformly diffusing light emitted from the light emitting diode is required.